Only 36 percent of those polled said they approved of Mr Bush's performance, down one percentage point from last November, according to the USA Today/CNN/Gallup poll.
Sixty percent of those surveyed said they disapprove of his performance in office.
The figure marks the lowest approval rating during Mr Bush's presidency.
Just 38 percent said they believe the almost three-year-old war is going well for the US, down from 46 percent in January, while 60 percent said they believe the war is going badly.
Fifty-seven percent said sending US troops to Iraq was a mistake, a rise of two percentage points since two weeks earlier, and close to the all-time high of 59 percent for that question, reached in September.
In an all-time high compared with previous polls, 67 percent said the president lacks "a clear plan for handling the situation in Iraq".
A similar percentage, however, did not believe the opposition Democrats have a clear plan either.
The poll, based on answers from 1,001 adults, reveals that Republicans face the potential threat of losing ground in Congress to Democrats in mid-term legislative elections in November.
When voters were asked which party they would support, Democrats scored 55 per cent to 39 per cent for the Republicans. The 16-point gap was the largest margin enjoyed by the Democrats since 1992, according to USA Today's website.
The poll results coincide with the launch of a fresh public relations campaign by Mr Bush, who is seeking to convince Americans that Iraq is not about to plunge into a full-blown civil war.